Online Etymology Dictionary

incommunicado (adj./adv.): 1844, American English, from Spanish incomunicado, past participle of incomunicar "deprive of communication," from in- "not" (see in- (1)) + comunicar "communicate," from Latin communicare "to share, impart" (see communication).
incomparability (n.): c. 1500, incomparablete, "quality of being peerless," from incomparable + -ity.
incomparable (adj.): early 15c., from Old French incomparable (12c.) or directly from Latin incomparabilis "that cannot be equaled," from in- "not" (see in- (1)) + comparabilis "comparable" (see comparable). Related: Incomparably.
incompatibility (n.): 1610s, from incompatible + -ity, or from French incompatibilité (15c.).
incompatible (adj.): "that cannot coexist or be conjoined," mid-15c., from Medieval Latin incompatibilis, from in- "not, opposite of" (see in- (1)) + compatibilis (see compatible). Originally of benefices, "incapable of being held together;" sense of "mutually intolerant" is from 1590s. Related: Incompatibly.
incompetence (n.): 1660s, "inadequacy;" 1716, "want of skill," from or modeled on French incompétence (16c.), from in- "not, opposite of, without" (see in- (1)) + compétence (see competence). Native formation incompetency is older (1610s).
incompetency (n.): 1610s, from incompetent + -cy.
incompetent (adj.): 1610s, "insufficient," from French incompétent, from Late Latin incompetentem (nominative incompetens) "insufficient," from in- "not" (see in- (1)) + Latin competentem (see competent). Sense of "lacking qualification or ability" first recorded 1630s. The noun meaning "incompetent person" is from 1866. Related: Incompetently.
incomplete (adj.): late 14c., from Late Latin incompletus "incomplete," from in- "not" (see in- (1)) + completus (see complete (adj.)). Related: Incompletely; incompleteness.
incompletion (n.): 1780, "incomplete condition," noun of state from incomplete. In reference to football passes, by 1926.
incomprehensibility (n.): 1590s, from incomprehensible + -ity; perhaps modeled on French incompréhensibilité (16c.).
incomprehensible (adj.): mid-14c., from Old French incomprehensible or directly from Latin incomprehensibilis "that cannot be seized or appreciated," from in- "not" (see in- (1)) + comprehensibilis (see comprehensible). Related: Incomprehensibly.
incomprehension (n.): c. 1600, from in- (1) "not" + comprehension.
incomprehensive (adj.): 1650s, from in- (1) "not, opposite of" + comprehensive. Related: Incomprehensively.
inconceivable (adj.): 1630s, from in- (1) "not, opposite of" + conceivable. Related: Inconceivably; inconceivability. An Old English word for this was unasmeagendlic.
inconclusive (adj.): 1660s, from in- (1) "not, opposite of" + conclusive. Related: Inconclusively. Inconclusion is "rare," perhaps because it could mean either "reaching no conclusion" or "reaching an unwarranted conclusion." Related: Inconclusiveness.
incondite (adj.): 1630s, "ill-made," earlier "crude, upolished" (1530s), from Latin inconditus "disordered, uncouth," from in- "not, opposite of" (see in- (1)) + conditus, past participle of condere "put together" (see abscond). Applied from 1845 to natural utterances ("oh!") from Latin (vox) incondita.
inconducive (adj.): 1729, from in- (1) "not, opposite of" + conducive.
incongruence (n.): c. 1600, from Late Latin incongruentia "incongruity," from incongruentem (nominative incongruens) "incongruous, inconsistent," from in- "not" (see in- (1)) + congruens (see congruent). Related: Incongruency.
incongruent (adj.): mid-15c., from Late Latin incongruentem (nominative incongruens), from in- "not" (see in- (1)) + congruens (see congruent). Related: Incongruently.
incongruity (n.): 1530s, "quality of being incongruent," from French incongruité (16c.) or directly from Medieval Latin incongruitas, from Latin in- "not" (see in- (1)) + congruitas (see congruity). Meaning "that which is incongruent, an example of incongruency" is from c. 1600.
incongruous (adj.): 1610s, from Latin incongruus "incongruous, inconsistent," from in- "not, opposite of, without" (see in- (1)) + congruus "fit, suitable" (see congruent). Related: Incongruously; incongruousness.
inconsequence (n.): 1580s, from Late Latin inconsequentia, from Latin inconsequens "inconsequent" (see inconsequent).
inconsequent (adj.): 1570s, "not following as a logical conclusion," from Latin inconsequentem (nominative inconsequens) "not logically connected, not resulting from what has preceded," from in- "not, opposite of, without" (see in- (1)) + consequens, past participle of consequi "to follow" (see consequence). Related: Inconsequently.
inconsequential (adj.): 1620s, "characterized by inconsequence;" 1782, "not worth noticing;" see inconsequent + -al (1). Related: Inconsequentially.
inconsiderable (adj.): 1590s, "incalculable;" from 1630s as "not worthy of consideration or notice," from French inconsidérable (16c.), from in- "not" (see in- (1)) + considérable (see considerable). Related: Inconsiderably. OED has found an instance of the rare verb inconsider from 1697.
inconsiderate (adj.): late 15c., "done thoughtlessly, heedless, careless, indiscreet," from Latin inconsideratus "headstrong, unadvised," of persons, "thoughtless," literally "not properly considered," from in- "not, opposite of" (see in- (1)) + consideratus (see consider). Sense of "without regard for the feelings of others" is from 1842. Related: Inconsiderately.
inconsiderateness (n.): 1590s, "imprudence," from inconsiderate + -ness. From 1858 as "want of consideration for others."
inconsideration (n.): 1520s, "indiscretion, rashness, failure to consider," from Late Latin inconsiderationem (nominative inconsideratio) "inconsiderateness," from Latin inconsideratus "headstrong, thoughtless" (see inconsiderate).
inconsistency (n.): 1640s, "something which is inconsistent;" 1650s as "quality of being inconsistent," from in- (1) "not, opposite of" + consistency. Related: Inconsistencies. Inconsistence (1630s) is marked "Now rare or Obs." in OED.
inconsistent (adj.): 1640s, "not agreeing in substance or form;" 1650s, "self-contradictory," from in- (1) "not, opposite of" + consistent. Related: Inconsistently.
inconsolable (adj.): 1590s, from Latin inconsolabilis "inconsolable," from in- "not" (see in- (1)) + consolabilis "consolable," from consolari (see console (v.)). Related: Inconsolably (c. 1500).
inconspicuous (adj.): 1620s, "invisible," from Late Latin inconspicuus "not conspicuous," from in- "not, opposite of, without" (see in- (1)) + Latin conspicuus (see conspicuous). Weakened sense of "not readily seen or noticed" developed by 1828. Related: Inconspicuously; inconspicuousness.
inconstance (n.): late 14c., from Old French inconstance "inconstancy, instability" (13c.), from Latin inconstantia "inconstancy, fickleness," noun of quality from inconstans "changeable, inconsistent" (see inconstant). In English, inconstancy is now the usual word.
inconstancy (n.): 1520s of persons, "fickleness;" 1610s of things, "mutability, irregularity," from Latin inconstantia "inconstancy, fickleness," noun of quality from inconstans "changeable, inconsistent" (see inconstant).
inconstant (adj.): c. 1400, "fickle, not steadfast," from Old French inconstant "variable, eccentric" (14c.), from Latin inconstantem (nominative inconstans) "changeable, fickle, capricious," from in- "not, opposite of, without" (see in- (1)) + constantem (see constant). Related: Inconstantly.
inconsumable (adj.): 1640s in reference to fire; 1785 in political economy; from in- (1) "not" + consumable. Inconsumptible is from 1570s.
inconsummate (adj.): "unfinished, incomplete," 1640s, from Late Latin inconsummatus "unfinished," from in- "not" (see in- (1) + consummatus "perfected, complete," past participle of consummare "sum up, to complete" (see consummation).
incontestable (adj.): 1670s, from in- "not" (see in- (1)) + contestable (see contest (v.)). Perhaps from or modeled on French incontestable. Related: Incontestably.
incontiguous (adj.): 1650s, from Late Latin incontiguus, from in- "not" (see in- (1)) + contiguus (see contiguous). Related: Incontiguously; incontiguousness.
incontinence (n.): late 14c., "inability to restrain sexual desire, sexual immorality," later "inability to keep to a religious rule" (early 15c.), from Old French incontinence "lack of abstinence, unchastity" (12c.) or directly from Latin incontinentia "greediness; incontinence, inability to contain," noun of quality from incontinens "incontinent, immoderate, intemperate" (see incontinent). Meaning "inability to restrain bodily functions" is from 1754.
incontinency (n.): early 15c., "unchastity;" see incontinent + -cy.
incontinent (adj.): late 14c., "wanting self-restraint," from Old French incontinent (14c.) or directly from Latin incontinentem (nominative incontinens) "immoderate, intemperate, not holding back," from in- "not, opposite of" (see in- (1)) + continens (see continent (adj.)). Originally chiefly of sexual appetites. General sense of "unable to retain" is from 1640s; medical sense of "unable to control bowels or bladder, unable to restrain natural discharges from the body" is attested by 1828.
He was incontynent, and with fleschely lustes he consumyd alle his tyme. ["Speculum Sacerdotale," 15th century]
incontinently (adv.): early 15c., "immediately, without delay, at once," from incontinent + -ly (2). From 1550s as "unchastely;" in reference to bodily discharges from 1847.
incontrovertible (adj.): 1640s, from in- (1) "not" + controvertible (see controvert). Related: Incontrovertibly; incontrovertibility.
inconvenience (v.): 1650s, from inconvenience (n.). Related: Inconvenienced; inconveniencing.
inconvenience (n.): c. 1400, "harm, damage; danger; misfortune, affliction," from Old French inconvenience "misfortune, calamity; impropriety" (Modern French inconvenance), from Late Latin inconvenientia "lack of consistency, incongruity" (in Medieval Latin "misfortune, affliction"), noun of quality from inconvenientem (see inconvenient). Sense of "impropriety, unfitness; an improper act or utterance" in English is from early 15c. Meaning "quality of being inconvenient" is from 1650s.
inconveniency (n.): early 15c., "calamity, injury, harmful consequence," also "danger" (now obsolete), from Late Latin inconvenientia (see inconvenience (n.)). Meaning "trouble, disadvantage, quality of being inconvenient" is from 1550s.
inconvenient (adj.): late 14c., "injurious, dangerous," also "absurd, illogical" (senses now obsolete), from Latin inconvenientem (nominative inconveniens) "unsuitable, not accordant, dissimilar," from in- "not, opposite of" (see in- (1)) + convenientem (see convenient). In early 15c., "inappropriate, unbecoming, unnatural;" also, of an accused person, "unlikely as a culprit, innocent." Sense of "troublesome, incommodious, awkward" first recorded 1650s.
inconveniently (adv.): mid-15c., "wrongfully," from inconvenient + -ly (2). Meaning "with trouble or discomfort" is from 1650s.